1. Field of the Invention
The present invention relates to a Stirling refrigerating system using a Stirling refrigerator, and particularly relates to a Stirling refrigerating system which is suitable for preservation of meat such as tuna, or long term preservation of cells, tissue, blood, etc., and which is large in size and capable of providing very low temperature.
2. Description of the Related Art
As a refrigerating system suitable for preservation of meat such as tuna, or for long-term preservation of cells, tissue, blood, etc., for example, a refrigerating system using flon as a refrigerant is known.
To cope with the recent flon regulation, a refrigerating system using HCFC (hydrochlorofluorocarbon) or HFC (hydrofluorocarbon), which is a CFC replacing material, is known.
In such conventional systems, however, there have been problems as follows.
First, in the refrigerating system using specified flon, that is, CFC (chlorofluorocarbon) as a refrigerant, the use of the specified flon is restricted by the flon regulation.
Also in the case of the refrigerating system using HCFC or HFC, there is a possibility that HCFC and HFC may be a subject of legal regulation in the future. In addition, there has been a problem that in view of the characteristics of the refrigerating system, its coefficient of performance is low and its energy efficiency is poor.
Therefore, it has been requested to develop a refrigerating system which has no fear that it will be subjected to such legal regulation, and which can refrigerate and preserve large-size frozen articles properly.